The present invention relates to a chain guide member such as a chain tensioner and a chain guide used in a chain transmission device, a manufacturing method thereof and a manufacturing apparatus thereof.
In a chain transmission device applied to a valve moving system of a four stroke cycle internal combustion engine, a chain tensioner for eliminating looseness of the chain or a chain guide for preventing disengagement of the chain from a sprocket has a sliding contact section coming into sliding contact with the chain. The sliding contact section is required to be made of a material having a good abrasion resistance and a low frictional resistance.
However, such a material is generally expensive and has low workability and low mechanical strength. Accordingly, in a chain guide member described in Japanese Patent No. 2818795, a reinforcement main body section of high mechanical strength and a sliding section of high abrasion resistance are piled up and extend in a chain traveling direction, and the reinforcement main body section and the sliding section are integrally connected through a dovetail joint.
According to the above-mentioned chain guide member of dovetail joint structure, the joint portion becomes necessarily thick from viewpoint of joint strength, the whole chain guide member is large-sized and cost-lowering and weight-reducing is difficult.
The chain guide member is manufactured in a manner that a supporting body with a dovetail key forming a greater part of the chain guide member is formed by injection, then a slide lining body is injected onto the support body. Therefore, when the slide lining body is formed by injection, temperature of the supporting member has been lowered, and resin for the slide lining body injected later comes into contact with the supporting body of low temperature to be cooled. As the result, the supporting body and the slide lining body are not joined integrally in a sufficiently melted state and the joint portion is weak.
In order to overcome the above-mentioned difficulties, the present invention provides a chain guide member having a sliding contact section extending along a traveling surface of a chain and coming into sliding contact with the chain and a reinforcement main body reinforcing and supporting the sliding contact section along the traveling surface of the chain, wherein a part or all of a joint portion between the sliding contact section and the reinforcement main body is joined by melting.
The sliding contact section and the reinforcement main body are connected to each other strongly, and miniaturization and cost-lowering of the chain guide member is possible.
The chain guide member may be made of thermoplastic resin. A cheap chain guide member having relatively high strength and good self-lubricating nature can be obtained.
The present invention provides a chain guide member manufacturing method, comprising steps of: partitioning a cavity of a mold by a partitioning member to form a space for forming a slide contact section of a chain guide member; injecting molten resin for the sliding contact section into the space; removing the partitioning member; and injecting molten resin for a reinforcement main body of the chain guide member into a remaining space of the cavity. According to the method, it is unnecessary to use respective molds for forming the sliding contact section and the reinforcement main body, and a chain guide member can be produced in a short time easily.
In the above chain guide member manufacturing method, a gas may be injected into the molten resin for the reinforcement main body injected into the cavity, a cave may be formed within the reinforcement main body in the cavity, and the reinforcement main body may be pressed against the sliding contact section by pressure of the gas within the cave. According to this method, the reinforcement main body and the sliding contact section can be connected more strongly and the chain guide member can be miniaturized.
The present invention provides a chin guide member manufacturing apparatus, comprising: a mold for forming a chain guide member; a partitioning member capable of going into a cavity of the mold to partition the cavity and form a space for a sliding contact section of the chain guide member; means for driving the partitioning member into the cavity; means for injecting molten resin for the sliding contact section into the space for the sliding contact section; and means for injecting molten resin for a reinforcement main body of the chain guide member into a space for the reinforcement main body in the cavity other than the space for the sliding contact section. According to this apparatus, the above-mentioned chain guide member manufacturing method can be carried out easily and surely.
The above manufacturing apparatus may include an opening for injecting molten resin for the slide contact section positioned on one end of the chain guide member, and an opening for injecting molten resin for the reinforcement main body positioned on another end of the chain guide member. According to this manufacturing apparatus, a portion of the resin for sliding contact section positioned near the opening for injecting molten resin for the reinforcement main body that has been injected most early and cooled is re-heated by molten resin for reinforcement main body injected from the opening for the reinforcement main body to prevent lowering of the temperature. On the other hand, a portion of the resin for the sliding contact section positioned near the opening for injecting resin for the sliding contact section that has been injected most lately is kept in relatively high temperature. As the result, temperature of the sliding contact section is kept substantially equal over the total length. Therefore, the sliding contact section resin and the reinforcement main body resin are melt-joined substantially equally and strongly along the total length of the chain guide member, and strength and durability of the chain guide member are improved remarkably.